Transmitter module, data transmission system and data transmission method

ABSTRACT

A transmitter module for a broadband data transmission system for radio communications, comprising at least one transmitter filter bank and a shaping module is described. The at least one transmitter filter bank is established as a synthesis polyphase FFT filter bank, wherein the transmitter module is configured to generate a transmission signal, wherein the transmitter module is configured to forward the transmission signal to the shaping module, wherein the shaping module is connected to the at least one transmitter filter bank downstream of the at least one synthesis polyphase FFT filter bank, and wherein the shaping module is configured to reduce a crest factor of the transmission signal. Moreover, a data transmission system and a data transmission method are described.

FIELD OF THE DISCLOSURE

The present disclosure is related to a transmitter module for abroadband data transmission system. The present disclosure is furtherrelated to a data transmission system as well as to a method for abroadband transmission of data.

BACKGROUND

Different techniques for a broadband transmission of data via radiofrequency are known from the state of the art. Examples for suchtechniques are direct sequence hopping, orthogonal frequency divisionmultiplexing and shaped orthogonal frequency division multiplexing.

For certain applications like police radio or military radio, it may bedesirable to reduce the crest factor of a signal that is to betransmitted in order to reduce the conspicuousness of the transmittedsignal.

One technique known in the art is direct polar clipping, where portionsof the signal exceeding a certain amplitude are simply cut off. However,this technique creates noise artifacts, so-called intermodulationproducts.

SUMMARY

There is a need to provide a transmitter module for a broadband datatransmission system as well as a method for a broadband transmission ofdata that improves the disadvantages from the state of the art.

To address this need or others, a transmitter circuit or module isprovided for a broadband data transmission system for radiocommunications. In an embodiment, the transmitter module comprises atleast one transmitter filter bank and a shaping circuit or module. Theat least one transmitter filter bank is established as a synthesispolyphase FFT filter bank. The transmitter module is configured togenerate a transmission signal. The transmitter module is configured toforward the transmission signal to the shaping module. The shapingmodule is connected to the at least one transmitter filter bankdownstream of the at least one synthesis polyphase FFT filter bank. Theshaping module is configured to reduce a crest factor of thetransmission signal.

The present disclosure is based on the finding that by providing anextra shaping module intermodulation products due to the crest factorreduction can be reduced. Thus, the shaping module is configured toreduce the crest factor of the transmission signal, resulting in reducednoise artifacts compared to the state of the art.

According to one aspect, the shaping module comprises a clipping circuitor module, wherein the clipping module is configured to reduce the crestfactor of the transmission signal, thereby generating a clippedtransmission signal. Generally speaking, the clipping module isconfigured to cut off signal portions whose amplitude exceeds a certainthreshold.

In some embodiments, the clipping module is established as a polarclipper. The polar clipper removes any portions of the transmissionsignal with an amplitude exceeding a certain threshold, regardless oftheir phase.

The shaping module may comprise a noise shaping circuit or module,wherein the noise shaping module is configured to remove intermodulationproducts from the clipped transmission signal. This way, noise artifactsin the transmission signal due to the crest factor reduction arereduced, resulting in a transmission signal with reduced crest factorand with attenuated intermodulation products.

The noise shaping module may comprise at least one noise shaping filterbank, wherein the noise shaping filter bank is established as asynthesis polyphase FFT filter bank. Generally speaking, the noiseshaping filter is configured to remove the intermodulation products fromthe clipped transmission signal by filtering out the respectivefrequency ranges corresponding to the intermodulation products. Thisway, noise artifacts from reducing the crest factor are attenuated.

According to another aspect, the noise shaping filter bank and thetransmitter filter bank are identical to one another. Therein, the term“identical” is to be understood to mean that the properties of theindividual parts of the noise shaping filter bank and of the transmitterfilter bank, for example the individual filter units comprised in thenoise shaping filter bank and on the transmitter filter bank areidentical. This does not mean, that the noise shaping filter bank andthe transmitter filter bank are two expressions for the same component.The noise shaping filter bank and the transmitter filter bank rather aredifferent components with identical properties. In other words, thenoise shaping filter bank and the transmitter filter bank match witheach other. It turned out that the quality of the generated transmissionsignal is greatly enhanced if the noise shaping filter bank and thetransmitter filter bank are identical to one another. For example, thegenerated transmission signal bears particularly small intermodulationproducts if the noise shaping filter bank and the transmitter filterbank are identical to one another.

According to another aspect, the noise shaping module comprises ananalysis polyphase FFT filter bank, wherein the analysis polyphase FFTfilter bank is connected to the noise shaping filter bank upstream ofthe noise shaping filter bank. The analysis polyphase FFT filter bankserves to split up the clipped transmission signal into its frequencycomponents. As the intermodulation products usually are situated ingeneric frequency ranges, they can be eliminated by filtering out thesespecific frequency ranges in a particularly simple manner.

The noise shaping module may comprise an orthogonal frequency divisionmultiplexing shape unit that is located between the analysis polyphaseFFT filter bank and the noise shaping filter bank. Via the orthogonalfrequency division multiplexing shape unit, the shape of the clippedtransmission signal is changed in such a way that the intermodulationproducts are further reduced.

In some embodiments, a delay circuit or module is provided that islocated in parallel to the noise shaping filter bank. The delay moduleadds a suitable amount of phase to the transmission signal such that thedelayed transmission signal and a signal processed by the shaping modulecan be combined correctly with respect to phase of the individualsignals.

In a further embodiment, the shaping module has two branch lines, forexample wherein the delay module is assigned to the first branch lineand/or at least one of the clipping module, the analysis polyphase FFTfilter bank, the orthogonal frequency division multiplexing unit and thenoise shaping filter bank is assigned to the second branch line. Thus,the first branch line transmits the transmission signal without anyclipping of the transmission signal, but with a delay. The second branchline transmits the clipped and/or filtered transmission signal.

In some embodiments, a subtraction circuit or unit is provided, whereinthe first branch line and the second branch line are both connected tothe subtraction unit. The subtraction unit is configured to subtract theclipped and/or filtered transmission signal from the transmissionsignal. This way, a clipped transmission signal with smallintermodulation products is obtained.

To further address this need or others, a data transmission system isprovided for a broadband transmission of data, comprising thetransmitter module described above. Regarding the advantages, referenceis made to the explanations given above with respect to the transmittermodule.

To further address this need or others, a data transmission method isprovided for a broadband transmission of data. In an embodiment, themethod comprises the following steps:

generating a transmission signal via transmitter filter bank that isestablished as a synthesis polyphase FFT filter bank;

clipping the transmission signal via a clipping module therebygenerating a clipped transmission signal;

subtracting the clipped transmission signal from the transmissionsignal, thereby generating a noise signal;

filtering the noise signal via a noise shaping filter bank, therebygenerating a filtered noise signal; and

subtracting the filtered noise signal from the transmission signal.

According to the present disclosure, the transmission signal is notsimply clipped. Instead, several intermediate steps are performed inorder to reduce intermodulation products. First, the transmission signalis clipped. The resulting clipped transmission signal bears the usualside-effects of the clipping, i.e. the intermodulation products. Theclipped transmission signal is subtracted from the transmission signal,wherein the resulting noise signal still bears the intermodulationproducts. Then, the intermodulation products are removed from the noisesignal by filtering the noise signal vie the noise shaping filter bank.Finally, the filtered noise signal is subtracted from the originaltransmission signal, resulting in a transmission signal with reducedcrest factor and with attenuated intermodulation products.

According to one aspect, the transmission signal is clipped via a polarclipper. The polar clipper removes any parts of the transmission signalwith an amplitude exceeding a certain threshold, regardless of theirphase.

According to another aspect, the noise shaping filter bank isestablished as a synthesis polyphase FFT filter bank. Thus, the noiseshaping filter bank has a similar or an identical set-up compared to thetransmitter filter bank. It turned out that the quality of the generatedtransmission signal is enhanced if the noise shaping filter bank and thetransmitter filter bank have similar or identical set-up.

In one embodiment, the noise shaping filter bank and the transmitterfilter bank are identical to one another. It turned out that the qualityof the generated transmission signal is greatly enhanced if the noiseshaping filter bank and the transmitter filter bank are identical to oneanother. For example, the generated transmission signal bearsparticularly small intermodulation products if the noise shaping filterbank and the transmitter filter bank are identical to one another.

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of theclaimed subject matter will become more readily appreciated as the samebecome better understood by reference to the following detaileddescription, when taken in conjunction with the accompanying drawings,wherein:

FIG. 1 schematically shows a block diagram of a data transmission systemaccording to an embodiment of the disclosure;

FIG. 2 shows an equivalent block diagram of a synthesis polyphase FFTfilter bank according to an embodiment of the present disclosure;

FIG. 3 shows a frequency response of a polyphase FFT filter bank;

FIG. 4 shows an equivalent block diagram of an analysis polyphase FFTfilter bank according to an embodiment of the present disclosure;

FIG. 5 shows a block diagram of a polyphaser FFT filter bank;

FIG. 6 schematically shows a block diagram of a transmitter moduleaccording to an embodiment of the disclosure;

FIG. 7 schematically shows a block diagram of a receiver moduleaccording to an embodiment of the disclosure;

FIG. 8 schematically shows a block diagram of a data transmission systemaccording to another embodiment of the disclosure;

FIG. 9 schematically shows a block diagram of a transmitter moduleaccording to another embodiment of the disclosure;

FIG. 10 schematically shows a block diagram of a receiver moduleaccording to another embodiment of the disclosure;

FIG. 11 schematically shows a block diagram of a transmitter moduleaccording to another embodiment of the disclosure; and

FIG. 12 schematically shows a flow chart of a method for a broadbandtransmission of data according to an embodiment of the disclosure.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings, where like numerals reference like elements, is intended as adescription of various embodiments of the disclosed subject matter andis not intended to represent the only embodiments. Each embodimentdescribed in this disclosure is provided merely as an example orillustration and should not be construed as preferred or advantageousover other embodiments. The illustrative examples provided herein arenot intended to be exhaustive or to limit the claimed subject matter tothe precise forms disclosed.

FIG. 1 shows a data transmission system 10 for a broadband transmissionof data via radio communication. The data transmission system 10comprises a transmitter circuit or module 12 and a receiver circuit ormodule 14. Generally speaking, the transmitter module 12 is configuredto generate and transmit a transmission signal, and the receiver module14 is configured to receive and process the transmission signal.

One or several such transmitter module(s) 12 and/or one or several suchreceiver module(s) 14 may be integrated on a common chip. Accordingly,the common chip is configured to generate a transmission signal and/orto receive and process the transmission signal. In some embodiments, thecommon chip is configured to generate, transmit and/or receive severaltransmission signals simultaneously via the several transmitter modules12 and/or the several receiver modules 14, respectively.

In some embodiments, the common chip is implemented as or otherwiseincludes a field programmable gate array (FPGA) or anapplication-specific integrated circuit (ASIC), for example. Of course,at least some of the functionality of the transmitter module(s) and/orthe receiver module(s) 14 can be carry out by discrete circuitcomponents, program code, or the like.

In the embodiment of FIG. 1, the transmitter module 12 comprises asignal generator circuit or module 16, a Tx processing circuit or module18 and a transmitter circuit or unit 20. The signal generator module 16is connected to the Tx processing module 18 in a signal transmittingmanner. The Tx processing module 18 in turn is connected to thetransmitter unit 20 in a signal transmitting manner.

The signal generator module 16 is configured to generate an inputsignal, wherein the input signal comprises a symbol sequence. The symbolsequence corresponds to the data and/or to a message that is to betransmitted from the transmitter module 12 to the receiver module 14.Therein and in the following, the term “symbol sequence” is to beunderstood to comprise a bit sequence, symbols of a PAM-n coded signaland/or any other type of coded information in the form of a sequence ofindividual symbols.

The Tx processing module 18 comprises at least one polyphase FFT filterbank that is established as a synthesis polyphase FFT filter bank 22.Generally speaking, the Tx processing module 18 is configured to receiveand process the input signal generated by the signal generator module16, thereby generating a processed input signal. Several embodiments ofthe Tx processing module and their more precise functionality will bedescribed in more detail below. All of these several embodiments have incommon that the Tx processing module 18 comprises the synthesispolyphase FFT filter bank 22.

The transmitter unit 20 is configured to receive the processed inputsignal, and to generate and transmit the transmission signal. Forexample, the transmitter unit 20 comprises at least one antenna, forexample at least one radio frequency antenna, that is configured totransmit the transmission signal. Of course, the transmitter unit 20 maycomprise several antennas, for example one or several antenna arrays.

In the embodiment of FIG. 1, the receiver module 14 comprises a frontend 24, an Rx processing circuit or module 26 and an output channel 28.The front end 24 is connected to the Rx processing module 26 in a signaltransmitting manner. The Rx processing module 26 in turn is connected tothe output channel 28 in a signal transmitting manner.

The front end 24 is configured to receive the transmission signal and toforward the transmission signal to the Rx processing module 26. Forexample, the front end comprises at least one antenna, for example atleast one radio frequency antenna, and suitable circuitry that isconfigured to receive the transmission signal. The front end 24 may alsocomprise several antennas, for example one or several antenna arrays.

The Rx processing module 26 comprises at least one polyphase FFT filterbank that is established as an analysis polyphase FFT filter bank 30.Generally speaking, the Rx processing module 26 is configured to receiveand process the transmission signal, thereby generating a processedtransmission signal. Moreover, the Rx processing module 26 is configuredto forward the processed transmission signal to the output channel 28.

Several embodiments of the Rx processing module 26 and their moreprecise functionality will be described in more detail below. All ofthese several embodiments have in common that the Rx processing module26 comprises an analysis polyphase FFT filter bank 30.

FIG. 2 shows an equivalent block diagram of the synthesis polyphase FFTfilter bank 22 of the Tx processing module 18. The synthesis polyphaseFFT filter bank 22 comprises several filter units 32. Each of the filterunits 32 is established as a bandpass filter, i.e. each of the filterunits 32 is associated with a specific frequency range that is able topass the respective filter unit 32, while the remaining frequency rangesoutside of the respective specific frequency range are filtered out.

In some embodiments, each of the filter units 32 is established as aNyquist filter, for example as a square-root-Nyquist-filter. Arepresentative frequency response of the synthesis polyphase filter bank22, more precisely of the several filter units 32, is shown in FIG. 3.

The frequency ranges associated with the individual filter units 32 aremutually different. In other words, the individual frequency ranges maypartially overlap each other, but their peaks are located at differentfrequencies.

In some embodiments, each of the individual frequency ranges forms aNyquist channel, i.e. the frequency response of each individual filterunit 32 has a zero at the peak of the frequency response of theneighbouring filter units 32. In other words, each of the filter units32 is associated with a sub-channel that corresponds to a subcarrier forthe transmission of the transmission signal. The subcarriers aremutually orthogonal in the sense as described above, i.e. the frequencyresponse of each individual filter unit 32 has a zero at the peak of thefrequency response of the neighbouring filter units 32.

Each of the filter units 32 has a M-fold oversampling, wherein M is aninteger bigger than one, for example an even integer bigger than one.This way, the filter units 32 can optimally process the input signalwhich is up-sampled with an up-sampling factor M/2, as is shown in FIG.3.

FIG. 4 shows an equivalent block diagram of the analysis polyphase FFTfilter bank 30. The analysis polyphase FFT filter bank 30 is establishedcomplementary to the synthesis polyphase FFT filter bank 22, in thesense that a concatenation of the synthesis polyphase FFT filter bank 22and the analysis polyphase FFT filter bank 30 yields a perfectreconstruction of the original signal.

In other words, if G(z) is the transfer function of the synthesispolyphase FFT filter bank 22 and H(z) is the transfer function of theanalysis polyphase FFT filter bank 30, it holds:

${{\sum\limits_{l}^{M}{{H(z)}{G(z)}}} = z^{- N}}.$

Accordingly, the analysis polyphase FFT filter bank 30 comprises thesame number of filter units 32 as the synthesis polyphase FFT filterbank 22. Moreover, the filter units 32 of the analysis polyphase FFTfilter bank 30 have the same frequency response as their respectivecounterpart filter unit 32 in the synthesis polyphase FFT filter bank22.

Put differently, the analysis polyphase FFT filter bank 30 and thesynthesis polyphase FFT filter bank 22 comprise pairwise identicalfilter units 32, i.e. for every filter unit 32 of the synthesispolyphase FFT filter bank 22, there is one identical filter unit 32 ofthe analysis polyphase FFT filter bank 30.

In the following, a first embodiment of the data transmission system 10,more precisely of the Tx processing module 18 and of the Rx processingmodule 26 will be described with reference to FIGS. 5 and 6,respectively.

FIG. 5 shows a block diagram of a polyphase FFT filter bank comprising atransmitter side with the synthesis polyphase FFT filter bank 22 and areceiver side with the analysis polyphase FFT filter bank 30. Thus, FIG.5 shows a block diagram of the components of the data transmissionsystem 10 from the synthesis polyphase FFT filter bank 22 to theanalysis polyphase FFT filter bank 30.

In the embodiment shown, both the synthesis polyphase FFT filter bank 22and the analysis polyphase FFT filter unit 30 each comprise a polyphaselow-pass filter (polyphase lowpass) and several buffer units (BUF).

As is depicted in FIG. 5, a signal x(n) received by the synthesis filterunit 22 is forwarded to several branches, wherein a different delay isapplied to the signal in every one of the branches, as is indicated by“Z⁻¹”. The signal is then filtered by the polyphase low-pass filter,buffered by the buffer units, up-sampled and finally Fourier transformedvia a fast Fourier transform (FFT).

Afterwards, the signal is digitally processed (digital signalprocessing, DSP), which is a collective term to represent allmanipulations of the signal between the synthesis polyphase FFT filterbank 22 and the analysis polyphase FFT filter bank 30. For example,“DSP” comprises sending the signal via the transmitter unit 20 andreceiving the signal via the front end 24.

On the receiver side, the signal is inversely fast Fourier transformed(IFFT), buffered by the buffer units, down-sampled and filtered by thepolyphase low-pass on the receiver side.

FIG. 6 shows the transmitter module 12 comprising the signal generatormodule 16 labelled as “symbol source”, the Tx processing module 18 andthe transmitter unit 20 labelled as “channel” in more detail. The Txprocessing module 18 comprises the synthesis polyphase FFT filter bank22, a hopping circuit or processor 34, a spread sequence generator 36, aspreading circuit or unit 38, an up-sampling circuit or unit 40 and aserial-to-parallel converter 42.

The hopping processor 34 is connected with the spread sequence generator36 in a signal transmitting manner. Moreover, the hopping processor 34is configured to control the spread sequence generator 36, as will bedescribed in more detail below.

Both the sequence generator 36 and the signal generator module 16 areconnected to the spreading unit 38 in a signal transmitting manner. Thespreading unit 38 comprises a mixer that is interconnected between thesignal generator module 16 and the sequence generator 36.

The transmitter module 12, more precisely the Tx processing module 18,is configured to perform the following method for generating theprocessed input signal:

The hopping processor 34 controls the spread sequence generator 36 togenerate a spread sequence. In some embodiments, the spread sequence isa Kasami sequence, preferably a cyclic shifted Kasami sequence asindicated in FIG. 6. The spread sequence is then forwarded to thespreading unit 38, for example the mixer.

The spreading unit 38, namely the mixer, receives both the spreadsequence and the input signal comprising the symbol sequence. Thespreading unit 38 then spreads the symbol sequence in frequency domainbased on the spread sequence by a direct sequence hopping spreadspectrum technique, thereby generating a spread input signal.

Put another way, the mixer receives and processes both the spreadsequence and the input signal comprising the symbol sequence such thatthe spread input signal is outputted.

The spread input signal is up-sampled with an up-sampling factor of twoby the up-sampling unit 40 and parallelized by theserial-to-parallel-converter 42.

The serial-to-parallel-converter 42 is connected to the synthesispolyphase FFT filter bank 22 such that each of the filter units 32 isconnected to the serial-to-parallel-converter 42. This way, the spreadinput signal is applied to every one of the filter units 32.

Accordingly, each one of the filter units 32 filters the spread inputsignal, and the filtered partial signals are then recombined, therebygenerating the transmission signal.

Therein, the hopping processor 34 controls the sequence generator 36 togenerate the spread sequence such that the spread input signal cannotsimultaneously pass filter units 32 that are adjacent to each other infrequency domain. In other words, the spreading sequence is generatedsuch that the transmitter module 12 sends only on every secondsubcarrier.

Put differently, the symbol sequence is spread in frequency by thespreading unit 38 and afterwards filtered by the filter units 32, suchthat every portion of the symbol sequence only passes through one of thefilter units 32 matching the frequency of the respective portion. Theoutput of each of the filter units 32 corresponds to a portion of thespread input signal having a certain frequency.

Combining these portions having different frequencies is tantamount to aFourier series. Thus, the transmission signal is the Fourier transformof the spread input signal. As shown in FIG. 6, the spread input signalis situated in frequency domain while the transmission signal issituated in time domain.

FIG. 7 shows the receiver module 14, more precisely the Rx processingmodule 26, according to the first embodiment of the data transmissionsystem 10.

In the embodiment of FIG. 7, the Rx processing module 26 comprises theanalysis polyphase FFT filter bank 30, a hopping circuit or processor44, a spread sequence generator 46, a de-spreading circuit or unit 48, adown-sampling circuit or unit 50, a parallel-to-serial converter 52 anda signal analysis circuit or module 54.

The receiver module 14, more precisely the Rx processing module 26 isconfigured to perform the following method for receiving and processingthe transmission signal received by the front end 24:

The transmission signal is first processed and analyzed via the signalanalysis module 54. For this purpose, the signal analysis module 54comprises at least one additional analysis polyphase FFT filter bank 56and at least one additional synthesis polyphase FFT filter bank 58.

The signal analysis module 54, more precisely the at least oneadditional analysis polyphase FFT filter bank 56 and the at least oneadditional synthesis polyphase FFT filter bank 58, is configured toanalyze a clock timing, a phase offset and/or a frequency offset of thereceived transmission signal.

Alternatively or additionally, the signal analysis module 56 may beconfigured to synchronize the receiver module 14 with the transmittermodule 12.

The signal analysis module 54 is configured such that the transmissionsignal is forwarded to the analysis polyphase FFT filter bank 30 in anessentially unaltered way, may be up to a multiplication with a phasefactor (for synchronizing the receiver module 14 with the transmittermodule 12).

As becomes apparent from FIG. 4, the transmission signal is forwarded toall filter units 32 of the analysis polyphase FFT filter bank 30.Accordingly, the transmission signal is filtered by each of the filterunits 32 and only the respective frequency components of thetransmission signal are able to pass. In other words, the analysispolyphase FFT filter bank 30 analyzes the frequency components of thetransmission signal, such that individual signals passing the individualfilter unit 32 correspond to the Fourier components of the transmissionsignal.

Accordingly, while the transmission signal is situated in time domain,the individual transmission signal components after the analysispolyphase FFT filter bank 30 are situated in frequency domain, asillustrated in FIG. 7.

Afterwards, the individual frequency components of the transmissionsignal are serialized by the parallel-to-serial converter 52, therebygenerating a serialized transmission signal.

Just like in the case of the transmitter module 12 described above, thehopping processor 44 of the receiver module 14 controls the spreadsequence generator 46 to generate a spread sequence. In someembodiments, the spread sequence is a Kasami sequence, preferably acyclic shifted Kasami sequence. The spread sequence is then forwarded tothe de-spreading unit 48, for example a mixer assigned to thede-spreading unit 48.

Therein, the hopping processor 44 of the receiver module 14 issynchronized with the hopping processor 34 of the transmitter module 12,such that the spread sequence generator 46 of the receiver module 14generates the same spread sequence as the spread sequence generator 36of the transmitter module 12, with an appropriate delay.

The de-spreading unit 48 receives both the spread sequence generated bythe spread sequence generator and the serialized transmission signal.The de-spreading unit 48 then de-spreads the serialized transmissionsignal, thereby recovering the input signal and the symbol sequencecomprised in the input signal.

Finally, the recovered input signal is down-sampled by the down-samplingunit 50, for example by a down-sampling factor M.

Summarizing, the data transmission system 10 described above isconfigured to transmit a signal and/or data via a direct sequencehopping spread spectrum technique. Thus, the carrier frequency fortransmitting the symbols comprised in the input signal is changed basedon the generated spread sequence, wherein only every second sub-carrieris used. This way, the different sub-channels do not interfere with oneanother and an enhanced transmission quality as well as an enhancedresilience against perturbations is achieved.

Using the data transmission system 10 described above, the transmissionsignal can even be transmitted, received and recovered with a negativesignal-to-noise-ratio (using a logarithmic scale).

The data transmission system 10 may be used by several users at the sametime, i.e. several users may transmit a respective transmission signalsimultaneously because the sub-channels used for the respectivetransmission do not interfere with each other.

The data transmission system 10 shown in FIGS. 6 and 7 can, without anychanges of hardware, also be adapted to perform an orthogonal frequencydivision multiplexing (OFDM) technique, for example a shaped orthogonalfrequency division multiplexing technique, which is explained in thefollowing with reference to the second embodiment of the datatransmission system 10 shown in FIG. 8.

Therein, parts or modules with like or similar functionality arelabelled with the same numerals as in FIGS. 6 and 7

The embodiment shown in FIG. 8 differs from the one shown in FIGS. 6 and7 in that no hopping processors 34, 44 and no spread sequence generators36, 46 are provided. However, the data transmission system 10 of FIGS. 6and 7 can be adapted to perform the (shaped) orthogonal frequencydivision multiplexing method by deactivating the hopping processors 34,44 and/or the spread sequence generators 36, 46.

The data transmission system 10 shown in FIG. 8 is configured totransmit a signal and/or data by the (shaped) orthogonal frequencydivision multiplexing technique on every second sub-channel, i.e. usingevery second sub-carrier, yielding the same advantages as describedabove.

Further, the data transmission system 10 may be configured to transmit apilot signal from the transmitter module 12 to the receiver module 14 onat least one of the free sub-channels, i.e. on at least one of thesub-channels that are not used for transmitting the transmission signal.

The pilot signal may then be used for determining a transfer function ofthe respective sub-channel that is used for transmitting the pilotsignal.

The determined transfer function can then be used to adapt the sendingcharacteristics, also called transmitting characteristics, and/or thereceiving characteristics of the transmitter module 12 and/or of thereceiver module 14, respectively.

In some embodiments, the data transmission system 10 may be configuredto interchange at least one of the transmission channels, i.e. at leastone of the sub-channels on which the transmission signal is transmitted,and the at least one pilot channel. This way, the sendingcharacteristics and/or the receiving characteristics of the transmittermodule 12 and/or of the receiver module 14 can be adapted for thesubsequent transmission of the transmission signal.

In the following, another embodiment of the data transmission system 10,more precisely of the Tx processing module 18 and of the Rx processingmodule 26 will be described with reference to FIGS. 9 and 10,respectively. Therein, parts or modules with like or similarfunctionality are labelled with the same numerals as in FIGS. 6 and 7.Moreover, only the differences with respect to the first embodiment ofthe data transmission system 10 will be described in the following.

FIG. 9 shows the transmitter module 12 comprising the signal generatormodule 16, the Tx processing module 18 and the transmitter unit 20 inmore detail. Like in the first embodiment, the Tx processing module 18comprises the synthesis polyphase FFT filter bank 22, a hoppingprocessor 34 and an up-sampling unit 40. The hopping processor 34 isinterconnected between the synthesis polyphase FFT filter bank 22 andthe up-sampling unit 40 in a signal transmitting manner.

Additionally, the Tx processing module 18 may comprise a fixed frequencycircuit or module 60 that is connected to the synthesis polyphase FFTfilter bank 30 in a signal transmitting manner.

The transmitter module 12, more precisely the Tx processing module 18,is configured for perform the following method for generating thetransmission signal:

As above, an input signal comprising a symbol sequence is generated bythe signal generator 16. The input signal is forwarded to theup-sampling unit 40 and up-sampled with an up-sampling factor of two.Then, the up-sampled input signal is forwarded to the hopping processor34.

The hopping processor 34 comprises several output channels, each ofwhich is connected to one of the filter units 32 of the synthesispolyphase FFT filter bank 22, respectively. Accordingly, the hoppingprocessor 34 controls to which of the filter units 32 the input signalis forwarded. Thus, the hopping processor 34 controls the momentarytransmission frequency of the transmission signal generated by thesynthesis polyphase FFT filter bank 22.

Just as described above, the transmission signal is then forwarded tothe transmitter unit 20 and is transmitted by the transmitter unit 20.

In other words, the transmitter module 12 is configured to transmit thetransmission signal based on the received input signal by a frequencyhopping technique.

Therein, the transmitter module 12 is configured to transmit thetransmission signal only on every second sub-channel, i.e. to only useevery second subcarrier.

The transmitter module 12 may be configured to transmit multipletransmission signals simultaneously, wherein each one of the multipletransmission signals is transmitted on another sub-channel. Once again,only every second sub-channel is used such that the several transmissionsignals do not interfere with each other.

Additionally, the transmitter module 12 may be configured to send on oneor several sub-channels with fixed frequency, i.e. without frequencyhopping. For this purpose, the fixed frequency module 60 is connected toone or several of the filter units 32 and is configured to forward thefixed frequency transmission signal to the one or several filter units32.

Thus, multiple users may send at the same time, wherein the hoppingprocessor 44 prevents a double occupancy of a single sub-channel.

Summarizing, the transmitter module 12 may be configured to transmit thetransmission signal or several transmission signals by a frequencyhopping technique and to additionally transmit the fixed frequencytransmission signal or several fixed frequency transmission channels,for example a hailing signal, by a fixed frequency transmissiontechnique.

FIG. 10 shows the receiver module 14, more precisely the Rx processingmodule 26, comprising the analysis polyphase FFT filter bank 30 in moredetail.

The Rx processing module 26 comprises a de-hopping processor 44, severaldown-sampling units 50 and a signal analysis module 54. The receivermodule 14, more precisely the Rx processing module 26 is configured toperform the following method for receiving and processing thetransmission signal received by the front end 24:

The transition signal is, just like in the embodiment described above,first processed and analyzed via the signal analysis module 54.Alternatively or additionally, the signal analysis module 54 may beconfigured to synchronize the receiver module 14 with the transmittermodule 12.

The signal analysis module 54 is configured such that the transmissionsignal is forwarded to the analysis polyphase FFT filter bank 30 in anessentially unaltered way, may be up to a multiplication with a phasefactor (for synchronizing the receiver module 14 with the transmittermodule 12).

The transmission signal is forwarded to all of the filter units 32 ofthe analysis polyphase FFT filter bank 30 simultaneously, such thatevery one of the filter units 32 receives the transmission signal.Accordingly, there is no need for an oscillator of the receiver module12 to adjust to the momentary transmission frequency, as all filterunits 32 receive the transmission signal at all times.

After being filtered by each of the filter units 32, the transmissionsignal is down-sampled by the down sampling units 50 and forwarded tothe de-hopping processor 44. The de-hopping processor 44 is synchronizedwith the hopping processor 34 and is configured to adjust a processingfrequency of the received transmission signal. In other words, thede-hopping processor 44 is configured to determine which transmissionsignal on which sub-channel is forwarded to the output channel 28. Thus,the de-hopping processor 44 determines a momentary receiving frequencythat matches the momentary transmission frequency such that thetransmission signal and the symbol sequence comprised in thetransmission signal can be received.

Moreover, the de-hopping processor 44 also determines, whether the fixedfrequency transmission signal is forwarded to the output channel 28.

Of course, multiple transmission signals can be received and processedat the same time, just as multiple transmission signals can be sent bythe transmitter module 12 at the same time.

Summarizing, the data transmission system 10 according to the thirdembodiment is configured to transmit a signal and/or data by a frequencyhopping technique. Thus, the hopping processor 34 determines themomentary transmission frequency, wherein only every second sub-carrieris used. This way, the different sub-channels do not interfere with oneanother and an enhanced transmission quality as well as an enhancedresilience against perturbations is achieved.

As all the filter units 32 of the receiver module 14 receive thetransmission signal at the same time, there is no need for an oscillatorto adjust to the momentary transmission frequency. Thus, no parts of thesignal are lost due to an adjustment time of the respective oscillators.

The data transmission system 10 may be used by several users at the sametime, i.e. several users may transmit a respective transmission signalsimultaneously because the sub-channels used for the respectivetransmission do not interfere with each other.

For the simultaneous transmission of several transmission signals,orthogonal hop-sets may be used such that the individual transmissionsof the respective users do not interfere with one another.

FIG. 11 shows a fourth embodiment of the transmitter module 12, moreprecisely of the Tx processing module 18. The Tx processing module 18comprises the synthesis polyphase FFT filter bank 22, one or severalup-sampling units 40 and a shaping circuit or module 62 that isconnected to the synthesis polyphase FFT filter bank 22 downstream ofthe synthesis polyphase FFT filter bank 22.

Generally speaking, the part of the Tx processing module 18 outside ofthe shaping module 62 is configured to generate a transmission signal byan orthogonal frequency division multiplexing technique, for example bya shaped orthogonal frequency division multiplexing technique.Accordingly, this part of the Tx processing module 18 may be establishedsimilar or identical to the one described above with reference to FIG. 6or FIG. 8.

Generally, the shaping module 62 is configured to reduce a crest factorof the transmission signal generated by the synthesis polyphase FFTfilter bank 22. In some embodiments, the shaping module 62 comprises aclipping circuit or module 64, a noise shaping circuit or module 66 anda delay circuit or module 68. In some embodiments, the clipping module64 is established as a polar clipper, i.e. it is configured to cut offparts of the transmission signal exceeding a certain thresholdamplitude.

The noise shaping module 66 comprises a noise shaping filter bank 70that is established as an synthesis polyphase FFT filter bank, forexample wherein the noise shaping filter bank 70 is establishedidentically to the synthesis polyphase FFT filter bank 22.

Moreover, the noise shaping module 66 further comprises an analysispolyphase FFT filter bank 72 that is connected to the noise shapingfilter bank 70 upstream of the noise shaping filter bank 70. Further,the noise shaping module 66 comprises an orthogonal frequency divisionmultiplexing (OFDM) shape unit 74 that is located between the analysispolyphase FFT filter bank 72 and the noise shaping filter bank 70.

As can be seen in FIG. 11, the shaping module 62 has two branch lines76, 78. The delay module 68 is assigned to the first branch line 76,while noise shaping module 66 is assigned to the second branch line 78,wherein the two branch lines 76, 78 are parallel to each other.

The Tx processing module 18 is configured to perform a method for abroadband transmission of data that is described in the following withreference to FIG. 12:

First, the transmission signal is generated by the synthesis polyphaseFFT filter bank 22 just as described above with respect to the firstembodiment of the data transmission system 10 (step S1).

The generated transmission signal is then forwarded to the clippingmodule 64 and to the delay module 68 (step S2). The delay module 68receives the generated transmission signal via the first branch line 76.

The clipping module 64 reduces the crest factor of the transmissionsignal by cutting off parts of the transmission signal exceeding thecertain amplitude, thereby generating a clipped transmission signal(step S3).

The clipped transmission signal is then subtracted from the transmissionsignal, thereby generating a noise signal (step S4), which is forwardedvia the second branch line 78.

The noise signal is then filtered via the noise shaping module 66,thereby generating a filtered noise signal (step S5). In step S5,intermodulation products are removed from the noise signal. In otherwords, the filtered noise signal comprises less noise artefacts from theclipping procedure in step S3 than the noise signal.

Parallel to steps S3 to S5, the transmission signal is delayed in asuitable manner by the delay module 68, thereby generating a delayedtransmission signal (step S6).

The delayed transmission signal was delayed in a manner so as to matchwith the filtered noise signal outputted by the noise shaping module 66.

Finally, the filtered noise signal is subtracted from the delayedtransmission signal (step S7).

The result of step S7 is a subtracted transmission signal that has asmaller crest factor compared to the transmission signal. Moreover, thesubtracted transmission signal bears less intermodulation productscompared to a method where the transmission signal is simply clippedwithout any further processing.

Certain embodiments disclosed herein utilize circuitry (e.g., one ormore circuits) in order to implement standards, protocols, methodologiesor technologies disclosed herein, operably couple two or morecomponents, generate information, process information, analyzeinformation, generate signals, encode/decode signals, convert signals,transmit and/or receive signals, control other devices, etc. Circuitryof any type can be used.

In an embodiment, circuitry includes, among other things, one or morecomputing devices such as a processor (e.g., a microprocessor), acentral processing unit (CPU), a digital signal processor (DSP), anapplication-specific integrated circuit (ASIC), a field-programmablegate array (FPGA), a system on a chip (SoC), or the like, or anycombinations thereof, and can include discrete digital or analog circuitelements or electronics, or combinations thereof. In an embodiment,circuitry includes hardware circuit implementations (e.g.,implementations in analog circuitry, implementations in digitalcircuitry, and the like, and combinations thereof).

In an embodiment, circuitry includes combinations of circuits andcomputer program products having software or firmware instructionsstored on one or more computer readable memories that work together tocause a device to perform one or more protocols, methodologies ortechnologies described herein. In an embodiment, circuitry includescircuits, such as, for example, microprocessors or portions ofmicroprocessor, that require software, firmware, and the like foroperation. In an embodiment, circuitry includes one or more processorsor portions thereof and accompanying software, firmware, hardware, andthe like.

The present application may reference quantities and numbers. Unlessspecifically stated, such quantities and numbers are not to beconsidered restrictive, but exemplary of the possible quantities ornumbers associated with the present application. Also in this regard,the present application may use the term “plurality” to reference aquantity or number. In this regard, the term “plurality” is meant to beany number that is more than one, for example, two, three, four, five,etc. The terms “about,” “approximately,” “near,” etc., mean plus orminus 5% of the stated value. For the purposes of the presentdisclosure, the phrase “at least one of A and B” is equivalent to “Aand/or B” or vice versa, namely “A” alone, “B” alone or “A and B.”.Similarly, the phrase “at least one of A, B, and C,” for example, means(A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C),including all further possible permutations when greater than threeelements are listed.

The principles, representative embodiments, and modes of operation ofthe present disclosure have been described in the foregoing description.However, aspects of the present disclosure which are intended to beprotected are not to be construed as limited to the particularembodiments disclosed. Further, the embodiments described herein are tobe regarded as illustrative rather than restrictive. It will beappreciated that variations and changes may be made by others, andequivalents employed, without departing from the spirit of the presentdisclosure. Accordingly, it is expressly intended that all suchvariations, changes, and equivalents fall within the spirit and scope ofthe present disclosure, as claimed.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A transmitter module fora broadband data transmission system for radio communications,comprising: at least one transmitter filter bank and a shaping module,wherein the at least one transmitter filter bank is established as asynthesis polyphase FFT filter bank, wherein the transmitter module isconfigured to generate a transmission signal, wherein the transmittermodule is configured to forward the transmission signal to the shapingcircuit, wherein the shaping circuit is connected to the at least onetransmitter filter bank downstream of the at least one synthesispolyphase FFT filter bank, and wherein the shaping circuit is configuredto reduce a crest factor of the transmission signal.
 2. The transmittermodule of claim 1, wherein the shaping circuit comprises a clippingcircuit, wherein the clipping circuit is configured to reduce the crestfactor of the transmission signal, thereby generating a clippedtransmission signal.
 3. The transmitter module of claim 2, wherein theclipping circuit is established as a polar clipper.
 4. The transmittermodule of claim 2, wherein the shaping circuit comprises a noise shapingcircuit, wherein the noise shaping circuit is configured to removeintermodulation products from the clipped transmission signal.
 5. Thetransmitter module of claim 4, wherein the noise shaping circuitcomprises at least one noise shaping filter bank, wherein the noiseshaping filter bank is established as a synthesis polyphase FFT filterbank.
 6. The transmitter module of claim 5, wherein the noise shapingfilter bank and the transmitter filter bank are identical to oneanother.
 7. The transmitter module of claim 5, wherein the noise shapingcircuit comprises an analysis polyphase FFT filter bank, wherein theanalysis polyphase FFT filter bank is connected to the noise shapingfilter bank upstream of the noise shaping filter bank.
 8. Thetransmitter module of claim 5, wherein the noise shaping circuitcomprises an orthogonal frequency division multiplexing shape unit thatis located between the analysis polyphase FFT filter bank and the noiseshaping filter bank.
 9. The transmitter module of claim 5, wherein adelay circuit is provided that is located in parallel to the noiseshaping filter bank.
 10. The transmitter module of claim 1, wherein theshaping circuit has two branch lines.
 11. The transmitter module ofclaim 10, wherein the delay circuit is assigned to the first branch lineand/or at least one of the clipping module, the analysis polyphase FFTfilter bank, the orthogonal frequency division multiplexing unit and thenoise shaping filter bank is assigned to the second branch line.
 12. Adata transmission system for a broadband transmission of data for radiocommunications, comprising the transmitter module according to claim 1.13. A data transmission method for a broadband transmission of data forradio communications, comprising: generating a transmission signal viatransmitter filter bank that is established as a synthesis polyphase FFTfilter bank; clipping the transmission signal via a clipping circuit,thereby generating a clipped transmission signal; subtracting theclipped transmission signal from the transmission signal, therebygenerating a noise signal; filtering the noise signal via a noiseshaping filter bank, thereby generating a filtered noise signal; andsubtracting the filtered noise signal from the transmission signal. 14.The data transmission method of claim 13, wherein the transmissionsignal is clipped via a polar clipper.
 15. The data transmission methodof claim 13, wherein the noise shaping filter bank is established as asynthesis polyphase FFT filter bank.
 16. The data transmission method ofclaim 15, wherein the noise shaping filter bank and the transmitterfilter bank are identical to one another.